There are many known bags for holding articles, including bags for storing and cooking food in microwave ovens. Popcorn, for example, is commonly packaged in gusseted bags that may be placed in a microwave oven to pop the popcorn. Such bags typically comprise front and back walls joined by gusseted side walls, with a microwave susceptor in one of the front and back walls for absorbing microwave energy and heating the contents of the bag. The gusseted side walls enable the bag to be folded flat for storage and shipment, but unfold and enable the bag to expand when the food inside the bag is cooked. The ends of the bag are closed and sealed by transverse bands of adhesive on the interior end surfaces of the front and back walls and the gusset folds. The bands of adhesive are applied during manufacture of the bag, and after the bag is folded to form a tubular structure with gusseted sides, heat and pressure is applied to the ends of the folded bag, thereby adhesively attaching the adjacent interior surfaces where the transverse bands of adhesive are located.
When the bag is in its folded flat condition, the inner folded edges of the gusseted side walls lie between the front and back walls and in spaced apart relationship to one another, whereby there are four layers of bag wall material along opposite sides of the bag, i.e., in the area where the gusset folds are interposed between the opposite side edges of the front and back walls, but there are only two layers of bag wall material along the longitudinal centerline of the bag, i.e., in the area between the inner edges of the gusset folds where the front and back walls are in opposed contiguous relationship. This difference in layers results in a transition in thickness, or a step, adjacent each inner folded edge of the gusseted sides. Where the gusset folds extend through the adhesive band forming the end closure of the bag, this step can result in a small unsecured area, or an area of weakened adhesive attachment, whereby a channel is formed, or can form, through the end closure, enabling cooking oil or other material to leak from the interior of the bag during and after cooking.
This specific problem has not been addressed in the prior art, although UK patent number 831,774 to HESSER recognized a similar problem where the longitudinal seam of a rectangular bag crosses the transverse seam closing the end of the bag. The bag in HESSER does not have gusseted side walls and therefore does not present the same problem that is solved by the present invention, i.e., to preclude the formation of an unsealed area or channel at the area where gusset folds extend through a bag end closure, to thereby prevent leakage of cooking oil or other material from the interior of the bag. HESSER appears to be primarily concerned with strengthening or reinforcing adhesively secured areas where a longitudinal seam crosses a transverse seam, especially at the exterior of the bag. See page 1, lines 26-35, 40-46 and 52-53. Further, HESSER appears to solve this problem by applying an additional layer of the heat sealable adhesive that is used to make the transverse and longitudinal seals in the bag. See page 2, lines 25-40.
U.S. Pat. No. 3,358,903 (De Stefano) and U.S. Pat. No. 5,461,261 (McDonald) address the problem of leakage through the walls or seams of gusseted bags, but De Stefano is concerned with leakage through longitudinal side seams formed in the medial fold of the gusseted side walls, and McDonald is concerned with leakage through the longitudinal folds of the gusseted side walls. Neither of these patents is concerned with the formation of channels where the gusset folds cross the end seam of a gusseted bag. De Stefano forms his bag by folding a web of material such that edges of the material are joined at seams extending longitudinally along the inner gusset folds, and reinforces this joint by applying extra adhesive, or using special folds, or extra adhesive and tape. McDonald addresses the problem of leakage through the longitudinal folded edges of the bag caused by damage to the fibers of the bag material when it is folded, and applies a strip or layer of adhesive in the crease of these folds to solve the problem.
U.S. Pat. No. 5,326,576 (Zuege) applies an extra patch of adhesive in the transverse seam at the top end of the bag to hold one side of the bag closed during filling, but he does not address the problem of leakage, nor would his extra patches of adhesive serve any useful function in this regard.
U.S. Pat. No. 4,691,374 (Watkins), U.S. Pat. No. 5,195,829 (Watkins), U.S. Pat. No. 5,498,080 (Dalea), U.S. Pat. No. 5,650,084 (Bley), U.S. Pat. No. 5,690,853 (Jackson), and U.S. Pat. No. 5,753,895 (Olson) all apply extra patches of adhesive in a location on the bag that generally coincides with the location of the bag end closure, but the extra patches of adhesive in these patents are applied externally of the bag rather than internally, and are for the purpose of preventing separation of the gussets at the bottom end of the bag, or forming a stiffening stay across the bottom, or to facilitate the formation of a square bottom, rather than for preventing leakage through the end closure.
Consequently, a need exists for an inexpensive and effective way of sealing and closing the channels or openings that may form through the bag end closure of a gusseted bag where the gusset folds extend through the closure, thereby preventing leakage of cooking oil or other material through the closure.